AD5535B

Data Sheet

Rev. A | Page 14 of 16

APPLICATIONS INFORMATION

MEMS MIRROR CONTROL APPLICATION

The AD5535B is targeted to all optical switching control systems

based on MEMS technology. The AD5535B is a 32-channel,

14-bit DAC with integrated high voltage amplifiers. The output

amplifiers are capable of generating an output range of 0 V to

200 V when using a 4 V reference. The full-scale output voltage

is programmable from 50 V to 200 V using reference voltages

from 1 V to 4 V. Each amplifier can output 550 µA and directly

drives the control actuators, which determine the position of

MEMS mirrors in optical switch applications.

The AD5535B is generally used in a closed-loop feedback system,

as shown in Figure 20, with a high resolution ADC and DSP.

The exact position of each mirror is measured using capacitive

sensors. The sensor outputs are multiplexed using an ADG739

4-to-1 multiplexer to an 8-channel, 14-bit ADC (AD7856). An

alternative solution is to multiplex using a 32-to-1 multiplexer

(ADG732) into a single-channel ADC (AD7671). The control

loop is driven by an ADSP-21065L, a 32-bit SHARC® DSP with

an SPI-compatible SPORT interface. With 14-bit monotonic

behavior and a 0 V to 200 V output range, coupled with its fast

serial interface, the AD5535B is ideally suited for controlling a

cluster of MEMS-based mirrors.

Figure 20. AD5535B in a MEMS-Based Optical Switch

IPC-221-COMPLIANT BOARD LAYOUT

The diagram in Figure 21 is a typical 2-layer printed circuit board

(PCB) layout for the AD5535B that complies with the specifications

outlined in IPC-221. Do not connect to the four corner balls

labeled as original no connects. Connect balls labeled as

additional no connects to AGND.

The routing shown in Figure 21 shows the feasibility of

connecting to the high voltage balls while complying with

the spacing requirements of IPC-221. Figure 21 also shows

the physical distances that are available.

Figure 21. Layout Guidelines to Comply with IPC-221

ADSP-21065L

AD5535B

OUTPUT RANGE

0V TO 200V

14-BIT DAC

14-BIT DAC

REF198

(4.096V)

ACTUATORS

FOR

MEMS

MIRROR

ARRAY

SENSOR

+

4-TO-1 MUX

(ADG739)

OR

32-TO-1 MUX

(ADG732)

8-CHANNEL

ADC (AD7856)

OR

SINGLE-

CHANNEL

ADC (AD7671)

+210V

+5V

REF_IN

A

B

C

D

E

F

G

J

H

K

L

M

N

P

10

8

7

6

3

2

1

9

5

4

11 12 13 14

1.414mm

2mm

250µm RAD

SPACE = 433µm

100µm

250µm RAD

SPACE = 433µm

SPACE = 433µm

100µm

DETAIL A

A1 BALL PAD CORNER

1

1

1

ORIGINAL

NO CONNECTS

ADDITIONAL

NO CONNECTS

1